Low pressure fluid supply system

Abstract

A fluid supply system includes a pump body having a main bore connectible through inlet check valves to draw fluid from a fluid reservoir and through outlet check valves to supply low pressure fluid to a low pressure function upon reciprocation of a free piston in the main bore. The free piston includes a pair of coaxial driving pistons on either side which extend into main passages which are alternately connected to a high pressure source to cause reciprocation of the free piston. A first spool valve which responds to the completion of a free piston stroke activates a second spool valve which changes the high pressure source connections to the driving pistons.

I claim: 
     
       1. A low pressure fluid supply system connectible to a high pressure fluid source, to a low pressure function and to a non-pressurized fluid reservoir, said low pressure fluid supply system comprising: (a) a pump body;   (b) a main bore enclosed within said pump body having a first and a second end;   (c) first and second bores enclosed within said pump body having respective first and second ends;   (d) a high pressure inlet into said pump body connecting said high pressure fluid source to said first and second bores between said respective first and second ends thereof;   (e) first and second pilot passages enclosed within said pump body respectively connecting said first bore proximate said first end to said second end of said second bore, and connecting said first bore proximate said second end to said first end of said second bore;   (f) first and second main passages enclosed within said pump body respectively connecting said second bore proximate said first end to said first end of said main bore, and connecting said second bore proximate said second end to said second end of said main bore;   (g) first and second control passages enclosed within said pump body respectively connecting said first and second ends of said first bore to said first and second main passages approximately at said ends of said main bore;   (h) first and second relief passages enclosed within said pump body respectively connecting said first end of said main bore to said first ends of both said first and second bores, and connecting said second end of said main bore to said second ends of both said first and second bore;   (i) a reservoir passage enclosed within said pump body connecting said non-pressurized fluid reservoir to both said first and second ends of said main bore;   (j) a low pressure passage enclosed within said pump body connecting said low pressure function to both said first and second ends of said main bore;   (k) first and second check valve means respectively disposed in said first and second ends of said main bore for preventing fluid from flowing from said main bore into said reservoir passage;   (l) third and fourth check valve means respectively disposed in said first and second ends of said main bore for preventing fluid from flowing from said low pressure passage into said main bore;   (m) first spool means positioned within said first bore and extending into both said first and second control passages, said first spool means movably responsive to high pressure fluid in said first control passage thereby connecting said high pressure fluid source to said first pilot passage and connecting said first relief passage to said second pilot passage; and movably responsive to high pressure fluid in said second control passage thereby connecting said high pressure fluid source to said second pilot passage and connecting said second relief passage to said first pilot passage;   (n) second spool means positioned within said second bore and extending into both said first and second pilot passages, said second spool means movably responsive to high pressure fluid in said first pilot passage thereby connecting said high pressure fluid source to said first main passage and connecting said second relief passage to said second main passage, and movably responsive to high pressure fluid in said second pilot passage thereby connecting said high pressure fluid source to said second main passage and connecting said first relief passage to said first main passage; and   (o) free piston means positioned within said main bore and extending in said first and second main passages, said free piston means for responding to high pressure fluid in said first main passage to move from a first position connecting said first control passage to said non-pressurized fluid reservoir and said second main passage to said low pressure fluid function through a series of positions for drawing fluid from said non-pressurized fluid reservoir through said first check valve means into said main bore and for urging fluid out of said main bore through said fourth check valve means to said low pressure fluid function while respectively blocking said first and second control passages from said non-pressurized fluid reservoir and said low pressure fluid function to a second position connecting said first control passage to said high pressure fluid source and said second main passage to said low pressure fluid function, said free piston means responsive to high pressure fluid in said second main passage to move from said second position through a series of positions to said first position thereby drawing fluid from said non-pressurized fluid reservoir through said second check valve means into said main bore and for urging fluid out of said main bore through said third check valve means to said low pressure fluid function.   
     
     
       2. A low pressure fluid supply system connectible to a high pressure pump, a fluid reservoir, and a low pressure function, said low pressure fluid supply system comprising: (a) a pump body;   (b) a main bore enclosed within said pump body having a first and a second end;   (c) first and second bores enclosed within said pump body having respective first and second ends;   (d) a high pressure inlet in said pump body connecting said high pressure pump to said first and second bores medially between said respective first and second ends thereof;   (e) first and second pilot passages enclosed within said pump body respectively connecting said first bore proximate said first end to said second end of said second bore, and connecting said first bore proximate said second end to said first end of said second bore;   (f) first and second main passages enclosed within said pump body respectively connecting said second bore proximate said first end to said first end of said main bore, and connecting said second bore proximate said second end to said second end of said main bore;   (g) first and second control passages enclosed within said pump body respectively connecting said first and second ends of said first bore to said first and second main passages approximately at said ends of said main bore;   (h) first and second relief passages enclosed within said pump body respectively connecting said first end of said main bore to said first ends of both said first and second bores, and connecting said second end of said main bore to said second ends of both said first and second bores;   (i) a reservoir passage enclosed within said pump body connecting said fluid reservoir to both said first and second ends of said main bore;   (j) a low pressure passage partially enclosed within said pump body connecting said low pressure function to both said first and second ends of said main bore;   (k) first and second check valves respectively disposed in said first and second ends of said main bore to prevent fluid from flowing from said main bore into said reservoir passage;   (l) third and fourth check valves respectively disposed in said first and second ends of said main bore to prevent fluid from flowing from said low pressure passage into said cylindrical main bore;   (m) a first spool slidably disposed in said first bore and having first and second ends, said first spool having first and second pilot pistons respectively extending from said first and second ends and respectively extending into said first and second control passages to move said first spool to a first position when said first and second control passages are respectively connected to said high pressure pump and said main bore, and to a second position when said first and second control passages are respectively connected to said main bore and to said high pressure pump, said first spool having land means for respectively connecting said first and second pilot passages to said high pressure inlet and to said first relief passage in said first position and respectively connecting said first and second pilot passages to said second relief passage and to said high pressure inlet in said second position;   (n) a second spool slidably disposed in said second bore and having first and second ends, said second spool having first and second pilot pistons respectively extending from said first and second ends and respectively extending into said first and second pilot passages to move said second spool to a first position when said first and second pilot passages are respectively connected to said main bore and to said high pressure pump, and to a second position when said first and second pilot passages are respectively connected to said high pressure pump and to said main bore, said second spool having land means for respectively connecting said first and second main passages to said high pressure inlet and to said second relief passage in said first position and respectively connecting said first and second main passages to said first relief passage and to said high pressure inlet in said second position; and   (o) a free piston slidably disposed in said main bore and having first and second ends, said free piston including first and second driving pistons respectively extending from said first and second ends and respectively extending into said first and second main passages to move said free piston to a first position when said first and second main passages are respectively connected to said high pressure pump and to said main bore, and to a second position when said first and second main passages are respectively connected to said main bore and to said high pressure pump, said free piston connecting said second main passage and said second control passage in said first position and connecting said first main passage and said first control passage in said second position while blocking the connections between said first and second positions, said free piston having relief means provided therein for connecting said first control passage to said main bore in said first position and said second control passage to said main bore in said second position.